1. Field of the Invention
The present invention relates to a pickup device that, for example, writes or reads data on and from, for example, an optical recording medium.
2. Description of Related Art
Various types of pickup devices are known which write or read data on and from an optical recording medium, e.g., optical disks such as DVDs (Digital Versatile Disks) and CDs (Compact Discs). Among these types of the pickup devices is one that radiates heat generated from a light source. A pickup device of this type includes a laser light source, a pickup base, and a heat-radiating unit. The laser light source is the light source for applying a light beam to an optical disk. The pickup base is a casing that contains the laser light source. The pickup device further includes optical elements. The optical elements are mounted on the pickup base. The optical elements are a beam splitter, a focusing lens, an optical detector, and the like. The beam splitter receives a laser beam emitted from the laser light source and reflects the laser beam toward an optical disk. The focusing lens focuses the laser beam. The optical detector detects a reflection light from the optical disk.
For example, the pickup base is made from metal material with high heat conductivity as the heat-radiating member that radiates the heat generated from the laser light source. If the pickup base is made of such metal, the heat generated by the laser light source is transmitted to the pickup base and radiated outside the device from the surface of the pickup base. Then, the heat does not accumulate in the laser light source. The laser light source is prevented from being deteriorated in the characteristics and shortened in the lifetime.
The heat-radiating member may be a heat-radiating plate with high heat conductivity that is adhered along the surface of the pickup base and abuts at one part thereof on the laser light source. A surface of the heat-radiating plate is adhered to the surface of the pickup base. In this case, the heat generated by the laser light source is transmitted to the heat-radiating plate and radiated outside the pickup device from the surface of the heat-radiating plate. By setting in close contact with the pickup base, the heat-radiating plate would not increase the size of the pickup device.
However, when the pickup base is made of metal material to function as a unit for radiating heat generated by the laser light source, the manufacturing cost of the pickup device will rise.
On the other hand, when the pickup base is made of synthetic resin that is less expensive than metal, and a heat-radiating plate for radiating heat generated by the laser light source is provided on the pickup base, the manufacturing cost will not increase. However, the pickup base made of synthetic resin cannot radiate heat from surface thereof, a radiating area will be only the surface of the heat-radiating plate which is exposed to the atmosphere. The heat-radiating efficiency is decreased due to the small heat-radiating area.
In recent years, laser light sources that can be used for both DVDs and CDs and laser light sources that can write data on optical disks have come into practical use. The amount of the heat from the laser light sources increases. The heat of the laser light source is not radiated sufficiently, since the laser light source has large amount of the heat but the pickup device has low heat-radiating efficiency.